| Title |
Bulk Niobium Polishing and Electropolishing Steps for Thinfilm Coated Copper SRF Cavities |
| Authors |
- M. Krishnan, S.F. Chapman, I. Irfan, K.M. Velas
AASC, San Leandro, California, USA
- J.K. Spradlin, H. Tian
JLab, Newport News, Virginia, USA
|
| Abstract |
Alameda Applied Sciences Corporation (AASC) grows Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. The plasma consists of 60-120eV Nb ions (Nb+ and Nb++) [1] that penetrate a few monolayers into the substrate [2] and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects) is accessible to the film [3]. One limitation of CED thinfilms is the presence of Nb macroparticles (~0.1-10 microns) that could be deleterious to high field performance of the SRF cavity. One way to remove such macroparticles [4] is to grow a thick film (~3-5 microns), followed by mechanical polishing (MP) using the finest media as might be applied in Centrifugal Barrel Polishing (CBP) to achieve a 0.4 micron surface figure, and an electropolishing (EP) step to remove ~1 micron of Nb that also removes all traces of embedded media in the film. The residual 2-4 micron Nb film should more nearly resemble the surface of a bulk Nb cavity that has been subjected to the same steps. This paper describes experiments conducted on Cu coupons as a prelude to an SRF Cu cavity coating.
|
| Funding |
Research supported at AASC by the US DOE via SBIR grant: DE-SC0011371. The JLab effort was provided by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 |
| Paper |
download TUPB034.PDF [1.431 MB / 5 pages] |
| Conference |
SRF2015, Whistler, BC, Canada |
| Series |
International Conference on RF Superconductivity (17th) |
| Proceedings |
Link to full SRF2015 Proccedings |
| Session |
Poster Session |
| Date |
15-Sep-15 14:30–17:40 |
| Main Classification |
Fundamentals SRF R&D - Other Materials |
| Keywords |
cavity, SRF, ion, plasma, cathode |
| Publisher |
JACoW, Geneva, Switzerland |
| Editors |
Robert E. Laxdal (TRIUMF, Vancouver, BC, Canada); Jana Thomson (TRIUMF, Vancouver, BC, Canada); Volker RW Schaa (GSI, Darmstadt, Germany) |
| ISBN |
978-3-95450-178-6 |
| Published |
December 2015 |
| Copyright |
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